Recently, interest of environment problems is increased and thus researches for fuel cells and the like are vigorously conducted as alternatives to gasoline engines and fossil-fuel generation. In order to increase availability of fuel cells, every condition should be provided, which can smoothly produce and/or feed hydrogen used in fuels.
Since hydrogen is the lightest among gases and can be easily exploded in air, its storage and handling are very difficult. Therefore, it is in the currently technical level to feed hydrogen simply using large volumes of hydrogen storage tanks. Such hydrogen storage tanks have disadvantages which are difficult to completely solve the previously mentioned problems.
In addition, there is a disadvantage that initial equipment investments such as developing large volumes of hydrogen storage tanks and preparing larger volumes of hydrogen reservoirs should be vastly required. It cannot help being such a vast project as would be discussed as infrastructures in a national level.
Therefore, a plan of miniaturizing a chemical reactor such as a reforming reactor producing hydrogen to reduce weight and volume is very desirable in that hydrogen may be used in clean fuels without requiring vast equipment investments.
Production apparatuses of hydrogen for feeding it into fuel cells roughly consist of three units. That is, they may be divided by a reformer for reforming fuels to produce hydrogen, carbon dioxide and carbon monoxide, a water gas shift reactor for reacting carbon monoxide with a steam to lower a concentration of carbon monoxide to 1% and increase a concentration of hydrogen, and a selective CO oxidation reactor for lowering a concentration of the remaining carbon monoxide to 10 ppm or less.
Especially, in case of a steam reforming reaction, the reaction is an endothermic reaction performed at a high temperature of 650° C. or more, and thus needs sustained heat supply. As heat supply sources, burners are used or catalytic combustion is utilized. In addition, the water gas shift reaction occurs at a temperature of 250 to 450° C., so that heat exchange of reformed gases discharged via the reformer is necessary.
Furthermore, when the catalytic combustion is utilized, it is advantageous to inject the pre-heated combustion gases, and also advantageous to pre-heat and inject the reforming fuels. For such pre-heating, separate pre-heaters should be used or the combustion gases or the reforming fuels should be heat-exchanged with burned stack gases or reforming gases exited from the reformer.
In KR Unexamined Patent Publication No. 1999-014655, a reformer, which could heat the reformer using combustion catalysts and simultaneously perform a function of developing steam and a function of pre-heating a mixture of air and fuels using heat of stack gases, was prepared. However, a heat exchanger is separately disposed so that heat loss occurred in the middle cannot be prevented. Therefore, it has disadvantages that heat efficiency is lowered and that the apparatus is complicated.
In U.S. Pat. No. 6,998,096 B2, a burner, a reformer, a heat exchanger and an evaporator were integrally constituted to increase heat efficiency. However, said technique has disadvantages that the reactor has so large volume that heat loss through wall surfaces cannot help being large, and the heat exchanger is positioned on top of the reformer and thus heat loss becomes large through the side wall surfaces of the relatively wide reformer.